There are two important points to consider.

The first thing is that you can't judge the stability of a kayak simply by the width. While it is obviously an important factor, other aspects of the design can have much more effect than most people realize. As the article below shows, it is possible for one kayak with a 24" beam to feel about four times as stable as another kayak with exactly the same beam.

http://www.blueheronkayaks.com/phpBB2/viewtopic.php?f=2&t=1825#p17806

Stability is also affected by the fineness of the bow and stern and the hull cross section.

The other thing is that a tall heavy paddler upsets the stability of a kayak much more than a short, light paddler.

However, the good news is that Tom's designs don't appear to sacrifice too much stability in an attempt to look sleek and stylish and at your height and weight, you will feel safe in a kayak that a much taller and heavier paddler would regard as slightly tippy.

The short answer is that I think you will be OK with your scaled down version.